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Superheterodyne Invention

July 8th Fact-of-the-Day

The earliest radio receivers consisted merely of RF amplitude-detectors of various kinds connected to antennas. The detectors were not called diodes at that time, but that is what they would be called today. Resonant circuits were placed between antennas and detectors as technology improved. They improved performance by providing a measure of frequency selection and better impedance matching. After Lee De Forest invented the triode vacuum tube in 1906, Tuned Radio Frequency amplifiers were added ahead detectors and TRF radios become 'state of the art'. In 1917 Edward Howard Armstrong applied Reginald Aubrey Fessenden's 1902 Heterodyne Signal Detection invention to the conversion of radio frequencies to intermediate frequencies, instead of to audio frequencies, called the process superheterodyne instead of heterodyne, patented the idea, and revolutionized the design of nearly all radios up until the present time. ©2005 Martek International All rights reserved.


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